Digitized image stabilization using energy analysis method

ABSTRACT

A method and an apparatus are provided for image stabilization for the output of analog-to-digital converters (ADC) and for phase-locked loops (PLL). The digital coding at the output of ADCs and PLLs is filtered by this method and apparatus to eliminate the noise which has contaminated the coding. The noise sources are noise picked up by the cable, system board noise, ADC power and ground noise paths, and switching noise. The differences of energy level of sequential pixels in the ADC and PLL digital outputs used in image displays are used to decide if correction is required. The method of image noise filtering is compatible with programmable circuitry. This allows the method to be tuned for optimal image stabilization.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to filtering noise effects outof digital signals using energy analysis of the digital coding. Moreparticularly, this invention relates to a method for image stabilizationfor the output of analog-to-digital converters and for phase-lockedloops.

2. Description of the Prior Art

Display images today often need stabilization and correction. Typically,this stabilization is required because of moving subjects or movingcameras. Without correction, the unstable images will be “fuzzy” or“blurred”. There are several techniques available in today's art. Theyinclude subdividing the image into nested pixel blocks in order todetermine the overall image change in magnification, rotation, andtranslation. This determined change could then be used to correct theoverall image. Another technique uses a sensor to detect the amount ofmovement of a display device and a correction circuit. Another techniqueuses displacement estimation and a feedback loop to achieve imagealignment.

FIG. 1 a shows an image display 11 with example pixels, x1, x2, x3, . .. , xn. In today's image processors, these individual pixels arenormally processed using analog-to-digital converters (ADC) andphase-locked loops (PLL). Today's art typically does not address theimage correction from the ADC and PLL circuit level.

-   -   U.S. Pat. No. 6,560,375 (Hathaway, et al.) describes a method of        stabilizing and registering a video image in multiple video        fields of a video sequence which provides accurate determination        of the image change in magnification, rotation and translation        between video fields, so that the video fields may be accurately        corrected for these changes in the image in the video sequence.        A key area of a video field is selected which contains an image        which it is desired to stabilize in a video sequence. The area        is subdivided into nested pixel blocks and the translation of        each of the pixel blocks from the video field to a new video        field is determined as a precursor to determining change in        magnification, rotation and translation of the image from the        key video field to the new video field.    -   U.S. Pat. No. 6,317,114 (Abali, et al.) discloses an image        stabilizing apparatus and method for a display device having a        display screen, include a sensor for sensing a movement of the        display device, and a movement compensation circuit, coupled to        the sensor, for compensating for the movement of the display        device such that an image on the display screen of the display        device remains stationary in relation to an observer's view.    -   U.S. Pat. No. 5,629,988 (Burt, et al.) describes a system and        method for electronic stabilization of an image produced by an        electronic imaging device. The input may be any sequence of        image frames from an image source, such as a video camera, an IR        or X-ray imager, radar, or from a storage medium such as        computer disk memory, videotape or a computer graphics        generator. The invention can also be used with images from        multiple sources when these must be stabilized with respect to        one another. The invention uses a feedback loop and second image        warp stage to achieve precise image alignment as part of the        displacement estimation process.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a methodand an apparatus for image stabilization for the output ofanalog-to-digital converters and for phase-locked loops.

The objects of this invention are achieved by a method of digitizedimage stabilization using energy analysis noise correction for analog-todigital converters (ADC). The method comprises the steps of determiningif a given image pixels' digital coding is not between the digitalcoding of its 2 adjacent pixels, and determining if differences betweena given image pixel's digital coding's absolute value and its twoadjacent pixel's digital coding is less than a pre-determined thresholdvalue. The image pixel's digital coding is determined to not be betweensaid coding of its two adjacent pixels in a monotonically increasingmode if the difference between a digital coding of a left-most adjacentpixel and the given image pixel is positive, and if the differencebetween the digital coding of the right-most adjacent pixel and thegiven image pixel is positive. The image pixel's digital coding isdetermined to not be between said coding of its two adjacent pixels in amonotonically decreasing mode if the difference between a digital codingof the left-most adjacent pixel and said given image pixel is negative,and if the difference between the digital coding of the right-mostadjacent pixel and said given image pixel is negative. If it has beendetermined that both a given image pixel's digital coding is not betweenthe digital coding of its 2 adjacent pixels and a difference betweengiven image pixel's digital coding's absolute value and its two adjacentpixel's digital coding is less than a pre-determined threshold value,than the digital coding of the given image pixel is changed to anaverage of the digital coding of the two adjacent pixels.

The objects of this invention are also achieved by a method of digitizedimage stabilization using energy analysis noise correction forphase-locked loops (PLL). The method comprises the steps of selecting anodd number, n, consecutive pixel samples which include a given imagepixel, (n−1)/2 consecutive image pixels which are adjacent on the leftto said given image pixel, and (n−1)/2 consecutive image pixels whichare adjacent on the right to said given image pixel. The method alsocomprises computing the (n−1) differences between digital codings ofsaid n consecutive pixel samples, adding said n−1 differences betweensaid digital codings of said n consecutive pixel samples to produce atotal energy, and choosing a programmable, threshold for the summationof said 4 differences between said digital codings of said n consecutivepixel samples. The method also comprises comparing said total energy tosaid threshold, deciding if said total energy is greater than saidthreshold, and changing said digital coding of said given image pixel ifsaid energy is greater than said threshold.

The above and other objects, features and advantages of the presentinvention will be better understood from the following detaileddescription taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a is a prior art view of an image display.

FIG. 1 b shows an analog-to-digital converter with the noise reductionapparatus of this invention.

FIG. 1 c shows a model of the noise reduction apparatus of thisinvention.

FIG. 2 a shows an energy analysis method for the output of an ADC tocorrect a pixel's digital coding upward toward more energy.

FIG. 2 b shows an energy analysis method for the output of an ADC tocorrect a pixel's digital coding downward toward less energy.

FIG. 2 c shows an energy analysis method for the output of an ADC whichis monotonically increasing and which does not qualify for correction.

FIG. 2 d shows an energy analysis method for the output of an ADC whichis monotonically decreasing and which does not qualify for correction.

FIG. 3 a shows a square wave output of a phase-locked loop which hasinconsistent digital coding.

FIG. 3 b shows a sine wave output of a phase-locked loop which hasinconsistent digital coding.

FIG. 4 a shows an energy analysis method for the output of a PLL tocorrect a pixel's digital coding upward toward more energy.

FIG. 4 b shows an energy analysis method for the output of a PLL tocorrect a pixel's digital coding downward toward less energy.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 b shows a block diagram of an analog signal 105 which isconverted to digital form using analog-to-digital converter, ADC 110.The output of the ADC consists of digital code 120. This digital codehas noise components which need to be removed. The noise components arecable noise, system board noise, ADC power and ground noise paths, andswitching noise. The ADC noise reduction block 130 is the location ofthe apparatus of this invention. The output 140 of the ADC noisereduction block is a “clean result” with minimal noise.

FIG. 1 c is a modeling block diagram. It shows a constant input value150. This constant or DC value goes into the ADC 155. Since the input isa DC value without noise, the ADC output is an Ideal output 170 withoutnoise. A noise source 160 is injected or added to the ADC clean outputat 165. The non-ideal digital output with noise is shown 175. The ADCnoise filter 180 of this invention removes the injected noise 160 toproduce clean result 190.

There are digital codes produced by an ADC for each of the display imagepixels displayed horizontally from left to right on a display. FIG. 2 ashows a plot of digital values versus horizontal position on a displayscreen. At horizontal position 1, there is a digital code of X1 (210).At horizontal position 2, there is a digital code X2 (230). Code X2(230) appeared at the output of the ADC block 130 in FIG. 1 a. The“gray” X2 code 240 is the adjusted code, which resulted from goingthrough the apparatus of this invention block 130 shown in FIG. 1 a.This “new” X2 (240) code is a result of averaging the adjacent codes X1(210) and X2 (220). X1, X2, and X3 represent 3 consecutive digital codesrepresenting 3 consecutive pixels displayed horizontally on a display.The equations for the averaging example shown in FIG. 2 a are asfollows.

Define E1 = G(x1) − G(x2) E2 = G(x3) − G(x2) If E1 > 0, E2 > 0, E1 <Ethreshold, and E2 < Ethreshold, then G(x2) = [G(x1) + G(x3)]/2 as inFIG. 2a.

As seen in the equations above, energy values E1 and E2 are definedbased on the differences of the absolute values of the digital codingsof horizontal pixels 1 and 2 and of the differences of the absolutevalues of the digital codings of horizontal pixels 3 and 2. Theequations above say that if E1 and E2 are positive and if E1 and E2 areboth less than some threshold, the digital coding of the middle pixel,x2 is replaced by the average of the digital coding of x1 and x3. If E1and E2 are not less than the threshold, there is no correction, sincethe coding of pixel x2 is probably valid. Also, if both E1 and E2 arenot greater than 0, the pixels are lined up as in either FIG. 2 c orFIG. 2 d and no correction is required. The example of FIG. 2 a is thecase where the “new” X2 (240) code resulting from ADC correction is more“white” with a higher value than the original X2 code 230.

FIG. 2 b shows a plot of digital values versus horizontal position on adisplay screen. At horizontal position 1, there is a digital code of X1(250). At horizontal position 2, there is a digital code X2 (270). CodeX2 (270) appeared at the output of the ADC block 130 in FIG. 1 a. The“gray” X2 code 280 is the adjusted code, which resulted from goingthrough the apparatus of this invention block 130 shown in FIG. 1 a.This “new” X2 (280) code is a result of averaging the adjacent codes X1(250) and X2 (260). X1, X2, and X3 represent 3 consecutive digital codesrepresenting 3 consecutive pixels displayed horizontally on a display.The equations for the averaging example shown in FIG. 2 b are asfollows.

Define E1 = G(x1) − G(x2) E2 = G(x3) − G(x2) If E1 < 0, E2 < 0,(absolute value E1) < Ethreshold, & (absolute value E2) < Ethreshold,then G(x2) = [G(x1) + G(x3)]/2 as in FIG. 2b.

As seen in the equations above, energy values E1 and E2 are definedbased on the differences of the absolute values of the digital codingsof horizontal pixels 1 and 2 and of the differences of the absolutevalues of the digital codings of horizontal pixels 3 and 2. Theequations above say that if E1 and E2 are positive and if E1 and E2 areboth less than some threshold, the digital coding of the middle pixel,x2 is replaced by the average of the digital coding of x1 and x3. If E1and E2 are not less than the threshold, there is no correction, sincethe coding of pixel x2 is probably valid. Also, if both E1 and E2 arenot greater than 0, the pixels are lined up as in either FIG. 2 c orFIG. 2 d and no correction is required. The example of FIG. 2 b is thecase where the “new” X2 (280) code resulting from ADC correction is more“white” with a higher value than the original X2 code 270.

FIG. 3 a shows the second or Phase Locked Loop (PLL) embodiment of thisinvention. FIG. 3 a shows an ideal PLL input analog waveform 310. Thesampling signals are shown 315. The actual PLL input, analog waveform isshown 320. The actual waveform has overshoots, undershoots, and samplingjitter. These irregularities cause the 8 bit digital code developed bydigital sampling to be inconsistent.

The 8-bit digital code for the sampling of the graph in FIG. 3 a isshown. For example, the first high level sample shown has a digitalvalue of ‘F9’ or (1111-1001). The second high level sample shown has adigital value of ‘F8’. The third high level sample shown has a digitalvalue of ‘FC’. All three high level samples yield different digitalcodings. This makes for an inconsistent digital representation comingout of the PLL. In addition, the first low-level sample shown has adigital value of ‘03’ or (0000-0011). The second low level sample shownhas a digital value of 05. The third low level sample shown has adigital value of low 01. All three level samples yield different digitalcodings. This results in inconsistent digital representations coming outof the PLL.

Similarly, FIG. 3 b shows a sine wave instead of the square wave 350shown in FIG. 3 a. In the example of FIG. 3 b, the effects of jitter onthe sampling position causes inconsistent digital codings. This samplingjitter can result in inconsistent and non-repeatable digital codings forthe same waveform as shown in FIG. 3 b.

FIG. 4 a shows a plot of energy level or gray level (G) versus theleft-to-right horizontal position of a pixel on a display. At horizontalposition 1, there is a digital code of X1 (410). At horizontal position2, there is a digital code X2 (450). At horizontal position 3, there isa digital code X3 (440). At horizontal position 4, there is a digitalcode X4 (460). At horizontal position 5, there is a digital code X5(420). The “gray” X3 code 430 is the adjusted code, which resulted fromgoing through the apparatus of this invention. This “new” X3 code is aresult of averaging the adjacent codes X1 (410) and X5 (420). This newX3 code is more “white” or higher up on the gray scale, as shown in FIG.4 a. This “white” example shown in FIG. 4 a represents the case of 5consecutive horizontal pixel samples. The reason for 5 consecutive pixelsamples is to utilize an even number of transitions (4) in order tocatch the Moiré pattern. A Moiré pattern of pixels are alternating whiteand black spots on the display. If more than 5 consecutive pixel samplesare used, more hardware would be needed to implement the apparatus ofthis invention. Therefore, 5 consecutive horizontal pixel samples isoptimum. The equation for the “white” example shown in FIG. 4 a is givenbelow.

Define: E1 = absolute value of [G(x1) − G(x2)] E2 = absolute value of[G(x2) − G(x3)] E3 = absolute value of [G(x3) − G(x4)] E4 = absolutevalue of [G(x4) − G(x5)] Energy = E1 + E2 + E3 + E4 If Energy >threshold (programmable), then G(x3) will be changed to “white value”(programmable), if G(x3) > 128

FIG. 4 b shows a plot of energy level or gray level (G) versus theleft-to-right horizontal position of a pixel on a display. At horizontalposition 1, there is a digital code of X1 (411). At horizontal position2, there is a digital code X2 (451). At horizontal position 3, there isa digital code X3 (441). At horizontal position 4, there is a digitalcode X4 (461). At horizontal position 5, there is a digital code X5(421). The “gray” X3 code 431 is the adjusted code, which resulted fromgoing through the apparatus of this invention. This “new” X3 code is aresult of averaging the adjacent codes X1 (411) and X5 (421). This newX3 code is more “black” or lower down on the grey scale, as shown inFIG. 4 b. This “black” example shown in FIG. 4 b represents the case of5 consecutive horizontal pixel samples. The reason for 5 consecutivepixel samples is to utilize an even number of transitions (4) in orderto catch the Moiré pattern. A Moiré pattern of pixels are alternatingwhite and black spots on the display. If more than 5 consecutive pixelsamples are used, more hardware would be needed to implement theapparatus of this invention. Therefore, 5 consecutive horizontal pixelsamples is optimum. The equation for the “black” example shown in FIG. 4b is given below.

Define: E1 = absolute value of [G(x1) − G(x2)] E2 = absolute value of[G(x2) − G(x3)] E3 = absolute value of [G(x3) − G(x4)] E4 = absolutevalue of [G(x4) − G(x5)] Energy = E1 + E2 + E3 + E4 If Energy >threshold (programmable), then G(x3) will be changed to “black value”(programmable), if G(x3) < 128.

The advantage of this invention is the unique energy analysis method ofimage stabilization and correction. The energy of image pixels arerepresented by the absolute values of the digital coding coming out ofan analog-to-digital converter or out of a phase-locked loop. Since theinvention involves comparing digital codes and digital thresholds, themethod is programmable and is amenable to be implemented via digitalcircuitry and processors.

While the invention has been described in terms of the preferredembodiments, those skilled in the art will recognize that variouschanges in form and details may be made without departing from thespirit and scope of the invention.

1. A method of digitized image stabilization using energy analysis noisecorrection for analog-to-digital converters (ADC) comprising the stepsof: determining if a given image pixels' digital coding is not betweenthe digital coding of its 2 adjacent pixels, determining if the absolutevalue of differences between a given image pixels digital coding and itstwo adjacent pixel's digital coding is less than a pre-determinedthreshold value, and using said image pixels' digital coding and saidabsolute value of differences to select which pixels result in a stableimage wherein said image is stabilized by calculating an optimumluminance using averaging and differences of light energy coding-wherein G(x1), G(x2), and G(x3) are digital codings of 3 consecutivepixels x1, x2, x3, wherein energy values, E1 and E2 are defined asE1=G(x1)−G(x2) E2−G(x3)−G(x2) and wherein Ethreshold is a variablethreshold chosen to optimize image stabilization, and wherein, If E1>0,E2>0, E1<Ethreshold, and E2<Ethreshold, then G(x2)=[G(x1)+G(x3)]/2. 2.The method of digitized image stabilization using energy analysis ofclaim 1 wherein said image pixel's digital coding is determined to notbe between said coding of its two adjacent pixels in a monotonicallyincreasing mode if the difference between a digital coding of aleft-most adjacent pixel and said given image pixel is positive, and ifthe difference between the digital coding of the right-most adjacentpixel and said given image pixel is positive.
 3. The method of digitizedimage stabilization using energy analysis of claim 1 wherein said imagepixel's digital coding is determined to not be between said coding ofits two adjacent pixels in a monotonically decreasing mode if thedifference between a digital coding of the left-most adjacent pixel andsaid given image pixel is negative, and if the difference between thedigital coding of the right-most adjacent pixel and said given imagepixel is negative.
 4. The method of digitized image stabilization usingenergy analysis of claim 1 wherein said difference between said givenimage pixel's digital coding's absolute value and its two adjacentpixel's digital coding's absolute value is determined for possibledigital coding correction, if said difference between said digitalcoding of said left-most adjacent pixel and said given pixel is lessthan said pre-determined threshold value, and if said difference betweensaid digital coding of said right-most adjacent pixel and said givenpixel is less than said pre-determined threshold value.
 5. The method ofdigitized image stabilization using energy analysis of claim 1 whereinif it has been determined that both a given image pixel's digital codingis not between the digital coding of its 2 adjacent pixels and adifference between given image pixel's digital coding's absolute valueand its two adjacent pixel's digital coding is less than apre-determined threshold value, then said digital coding of said givenimage pixel is changed to an average of said digital coding of said twoadjacent pixels.
 6. The method of digitized image stabilization usingenergy analysis of claim 1 wherein if it has been determined that agiven image pixel's digital coding is not between the digital coding ofits 2 adjacent pixels, and a difference between given image pixel'sdigital coding's absolute value and its two adjacent pixel's digitalcoding is less than a pre-determined threshold value, then the digitalcoding of said given pixel is not changed and is kept to the originaldigital coding of said given image pixel.
 7. The method of digitizedimage stabilization using energy analysis of claim 1 wherein saidpre-determined threshold value is set to two or three least significantbits, in order to filter out ADC noise.
 8. A method of digitized imagestabilization using energy analysis noise correction forphase-locked-loops (PLL) comprising the steps of: selecting an oddnumber, n, consecutive pixel samples which include a given image pixel,(n−1)/2 consecutive image pixels which are adjacent on the left to saidgiven image pixel, and (n−1)/2 consecutive image pixels which areadjacent on the right to said given image pixel, computing the n−1differences between digital codings of said n consecutive pixel samples,adding said n−1 differences between said digital codings of said nconsecutive pixel samples, to produce a total energy, choosing aprogrammable, threshold for the summation of said n−1 differencesbetween said digital codings of said n consecutive pixel samples,comparing said total energy to said threshold, deciding if said totalenergy is greater than said threshold, and changing said digital codingof said given image pixel if said energy is greater than said threshold,resulting in a stable image.
 9. The method of digitized imagestabilization using energy analysis noise correction for phase-lockedloops (PLL) of claim 8 wherein said samples are chosen to provide aneven number of transitions.
 10. The method of digitized imagestabilization using energy analysis noise correction for phase-lockedloops (PLL) of claim 8 wherein said ‘n’ consecutive pixel samples arechosen to be five to balance hardware complexity and effectiveness inrepresenting alternating black and white images.
 11. The method ofdigitized image stabilization using energy analysis noise correction forphase-locked loops (PLL) of claim 8 wherein said (n−1) differencesbetween digital codings of said n consecutive pixel samples are computedby subtracting a digital coding of a second pixel from a digital codingof a first pixel and a digital coding of a third pixel from said digitalcoding of said second pixel, wherein generally a digital coding of anx+1 pixel is subtracted from a digital coding of an x pixel, where x=1,2, 3, . . . n.
 12. The method of digitized image stabilization usingenergy analysis noise correction for phase-locked loops (PLL) of claim11 wherein said n−1 differences between said digital codings are addedto produce a total energy value.
 13. The method of digitized imagestabilization using energy analysis noise correction for phase-lockedloops (PLL) of claim 8 wherein said programmable threshold is chosen todistinguish smooth low contrast images from high contrast images such asalternating black and white images.
 14. The method of digitized imagestabilization using energy analysis noise correction for phase-lockedloops (PLL) of claim 12 wherein said total energy value is compared tosaid programmable threshold.
 15. The method of digitized imagestabilization using energy analysis noise correction for phase-lockedloops (PLL) of claim 14 where if said total energy value is greater thansaid programmable threshold, a “change pixel coding flag is set.
 16. Themethod of digitized image stabilization using energy analysis noisecorrection for phase-locked loops (PLL) of claim 15 wherein if saidchange pixel coding flag is set, said digital coding of said given imagepixel is changed to a white value if said digital coding of said givenimage pixel is greater than a white threshold.
 17. The method ofdigitized image stabilization using energy analysis noise correction forphase-locked loops (PLL) of claim 16 wherein if said change pixel codingflag is set, said digital coding of said given image pixel is changed toa black value if said digital coding of said given image pixel is lessthan said white threshold.
 18. An apparatus for digitized imagestabilization using energy analysis noise correction for analog-todigital converters (ADC) comprising: a means for determining if a givenimage pixels' digital coding is not between the digital coding of its 2adjacent pixels, a means for determining if the absolute value ofdifferences between a given image pixel's digital coding and its twoadjacent pixels digital coding is less than a pre-determined thresholdvalue, and a means for using said image pixels' digital coding and saidabsolute value of differences to select which pixels result in a stableimage, wherein said image is stabilized by calculating an optimumluminance using averaging and differences of light energy coding-wherein G(x1), G(x2), and G(x3) are digital codings of 3 consecutivepixels x1, x2, x3, wherein energy values, E1 and E2 are defined asE1=G(x1)−(x2) E2−G(x3)−G(x2) and wherein Ethreshold is a variablethreshold chosen to optimize image stabilization, and wherein, If E1>0,E2>0, E1<Ethreshold, and E2<Ethreshold, then G(x2)=[G(x1)+G(x3)]/2. 19.The apparatus for digitized image stabilization using energy analysis ofclaim 18 wherein said image pixel's digital coding is determined to notbe between said coding of its two adjacent pixels in a monotonicallyincreasing mode if the difference between a digital coding of aleft-most adjacent pixel and said given image pixel is positive, and ifthe difference between the digital coding of the right-most adjacentpixel and said given image pixel is positive.
 20. The apparatus fordigitized image stabilization using energy analysis of claim 18 whereinsaid image pixel's digital coding is determined to not be between saidcoding of its two adjacent pixels in a monotonically decreasing mode ifthe difference between a digital coding of the left-most adjacent pixeland said given image pixel is negative, and if the difference betweenthe digital coding of the right-most adjacent pixel and said given imagepixel is negative.
 21. The apparatus for digitized image stabilizationusing energy analysis of claim 18 wherein said difference between saidgiven image pixel's digital coding's absolute value and its two adjacentpixel's digital coding's absolute value is determined for possibledigital coding correction, if said difference between said digitalcoding of said left-most adjacent pixel and said given pixel is lessthan said pre-determined threshold value, and if said difference betweensaid digital coding of said right-most adjacent pixel and said givenpixel is less than said pre-determined threshold value.
 22. Theapparatus for digitized image stabilization using energy analysis ofclaim 18 wherein if it has been determined that both a given imagepixel's digital coding is not between the digital coding of its 2adjacent pixels and a difference between given image pixel's digitalcoding's absolute value and its two adjacent pixel's digital coding isless than a pre-determined threshold value, then said digital coding ofsaid given image pixel is changed to an average of said digital codingof said two adjacent pixels.
 23. The apparatus for digitized imagestabilization using energy analysis of claim 18 wherein if it has beendetermined that a given image pixel's digital coding is not between thedigital coding of its 2 adjacent pixels, and a difference between givenimage pixel's digital coding's absolute value and its two adjacentpixel's digital coding is less than a pre-determined threshold value,then the digital coding of said given pixel is not changed and is keptto the original digital coding of said given image pixel.
 24. Theapparatus for digitized image stabilization using energy analysis ofclaim 18 wherein said pre-determined threshold value is set to two orthree least significant bits, in order to filter out ADC noise.
 25. Aapparatus for digitized image stabilization using energy analysis noisecorrection for phase-locked-loops (PLL) comprising: means for selectingan odd number, n, consecutive pixel samples which include a given imagepixel, (n−1)1/2 consecutive image pixels which are adjacent on the leftto said given image pixel, and (n−1)1/2 consecutive image pixels whichare adjacent on the right to said given image pixel, means for computingthe n−1 differences between digital codings of said n consecutive pixelsamples, means for adding said n−1 differences between said digitalcodings of said n consecutive pixel samples, to produce a total energy,means for choosing a programmable, threshold for the summation of saidn−1 differences between said digital codings of said n consecutive pixelsamples, means for comparing said total energy to said threshold, meansfor deciding if said total energy is greater than said threshold, andmeans for changing said digital coding of said given image pixel if saidenergy is greater than said threshold, resulting in a stable image. 26.The apparatus for digitized image stabilization using energy analysisnoise correction for phase-locked loops (PLL) of claim 25 wherein saidsamples are chosen to provide an even number of transitions.
 27. Theapparatus for digitized image stabilization using energy analysis noisecorrection for phase-locked loops (PLL) of claim 25 wherein said ‘n’consecutive pixel samples are chosen to be five to balance hardwarecomplexity and effectiveness in representing alternating black and whiteimages.
 28. The apparatus for digitized image stabilization using energyanalysis noise correction for phase-locked loops (PLL) of claim 25wherein said (n−1) differences between digital codings of said nconsecutive pixel samples are computed by subtracting a digital codingof a second pixel from a digital coding of a first pixel and a digitalcoding of a third pixel from said digital coding of said second pixel,wherein generally a digital coding of an x+1 pixel is subtracted from adigital coding of an x pixel, where x=1, 2, 3, . . . n.
 29. Theapparatus for digitized image stabilization using energy analysis noisecorrection for phase-locked loops (PLL) of claim 28 wherein said n−1differences between said digital codings are added to produce a totalenergy value.
 30. The apparatus for digitized image stabilization usingenergy analysis noise correction for phase-locked loops (PLL) of claim25 wherein said programmable threshold is chosen to distinguish smoothlow contrast images from high contrast images such as alternating blackand white images.
 31. The apparatus for digitized image stabilizationusing energy analysis noise correction for phase-locked loops (PLL) ofclaim 29 wherein said total energy value is compared to saidprogrammable threshold.
 32. The apparatus for digitized imagestabilization using energy analysis noise correction for phase-lockedloops (PLL) of claim 31 where if said total energy value is greater thansaid programmable threshold, a “change pixel coding flag is set.
 33. Theapparatus for digitized image stabilization using energy analysis noisecorrection for phase-locked loops (PLL) of claim 32 wherein if saidchange pixel coding flag is set, said digital coding of said given imagepixel is changed to a white value if said digital coding of said givenimage pixel is greater than a white threshold.
 34. The apparatus fordigitized image stabilization using energy analysis noise correction forphase-locked loops (PLL) of claim 33 wherein if said change pixel codingflag is set, said digital coding of said given image pixel is changed toa black value if said digital coding of said given image pixel is lessthan said white threshold.